Process and system for improving light olefin yield and feedstock utilization from C5 raffinate stream

Abstract

Systems and methods for producing light olefins from liquefied natural gas (NGL) or other C5 streams are provided. The process can include supplying an NGL or other C5 stream to a reverse isomerization unit to produce an n-pentane enriched NGL stream, and supplying the n-pentane enriched NGL stream to a liquid furnace to produce a pyrolysis product stream. The method may also include separating C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6 + hydrocarbons in the pyrolysis product stream in a separation sequence, and supplying the separated C5 hydrocarbons, or a portion thereof, to a hydrogenation reactor to produce a saturated C5 hydrocarbon stream, followed by recycling the saturated C5 hydrocarbon stream to the reverse isomerization unit.

Description

Technical Field

[0001] The present invention generally relates to systems and methods for increasing the yield of light olefins and feedstock utilization from natural gas liquids (NGLs) or other C5 streams. More specifically, among other embodiments, the present invention relates to systems and methods for improving the production of ethylene from an NGL feed stream by hydrogenating a C5 raffinate stream and then recycling the saturated C5 raffinate stream to a reverse isomerization reactor to increase the n-C5 feed to the furnace. The hydrogenation can be carried out independently or together with a C4 stream. Background Art

[0002] Ethylene is a desirable industrial compound with a world production higher than any other organic compound. Thus, ethylene is widely used in the chemical industry, particularly as a feedstock for the production of polyethylene. Among other production methods, ethylene can be produced by the pyrolysis of natural gas liquids (NGLs) and / or other C5 streams in a liquid furnace or cracker. The main components of NGLs are mixed pentanes, typically about 50% n-C5 and 43% i-C5, with the specific composition varying from well to well. The pyrolysis liquid furnace can be used to crack the NGL feedstock into high-value olefins such as ethylene, propylene, benzene, butadiene, and a C5 raffinate. The lighter olefins, for which there is a greater demand, are particularly desirable, so enhancing the light olefin yield of the pyrolysis liquid furnace increases the overall profitability of the process. In recent years, the modern chemical industry has focused on minimizing carbon losses and maximizing productivity in terms of energy sustainability. Thus, methods and systems are desired that can improve the efficiency of light olefin production, particularly ethylene production, and improve the feedstock utilization of NGL-derived streams. Summary of the Invention

[0003] To address these drawbacks in the art, according to the exemplary embodiments disclosed herein, the applicant has developed systems and methods for increasing the yield of light olefins from the pyrolysis of an NGL stream or other C5 stream in a liquid furnace by upgrading the feedstock prior to injection into the liquid furnace. Specifically, among other exemplary embodiments, the applicant has developed systems and methods for downstream recycling or preprocessing of an NGL hydrocarbon feedstock that use one or more hydrogenation reactors, carried out independently or together with a C4 stream, and a reverse isomerization reactor to provide a rich n-C5 feedstock stream to the pyrolysis furnace, thereby increasing the overall productivity of light olefins, particularly ethylene.

[0004] Systems and methods for producing light olefins from a natural gas liquid (NGL) stream are provided. In certain embodiments, a method for producing light olefins from an NGL stream may include: supplying an NGL stream to a reverse isomerization unit to produce a pentane-enriched NGL stream; supplying the pentane-enriched NGL stream to a liquid furnace or one or more pyrolysis furnaces to produce a pyrolysis product stream that includes C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons; separating the C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons in the pyrolysis product stream in a separation train; supplying the separated C5 hydrocarbons or a portion thereof to a first hydrogenation reactor to produce a saturated or hydrogenated C5 hydrocarbon stream; and recycling the saturated or hydrogenated C5 hydrocarbon stream to the reverse isomerization unit.

[0005] In some embodiments of the method, recycling the saturated or hydrogenated C5 hydrocarbon stream to the reverse isomerization unit increases the light olefin yield, particularly the ethylene and / or propylene yield, of the liquid furnace or one or more liquid furnaces. In some embodiments, the NGL stream may be formed by the combination of a fresh natural gas liquid feed and the saturated or hydrogenated C5 hydrocarbon stream produced in the first hydrogenation reactor. In some embodiments of the method, the method may further include supplying the separated C4 hydrocarbons or a portion thereof to a second hydrogenation reactor to produce a saturated or hydrogenated C4 hydrocarbon stream, and recycling the saturated or hydrogenated C4 hydrocarbon stream to the reverse isomerization unit.

[0006] In some embodiments, the method may further include supplying the separated C4 hydrocarbons or a portion thereof to the first hydrogenation reactor to produce a combined saturated or hydrogenated C4 hydrocarbon and saturated or hydrogenated C5 hydrocarbon stream. In some embodiments, the method may further include recycling the combined saturated or hydrogenated C4 and C5 hydrocarbon stream to the reverse isomerization unit. In some embodiments, the NGL stream may be formed by the combination of a fresh natural gas liquid feed and the combined saturated or hydrogenated C4 and C5 hydrocarbon stream produced in the first hydrogenation reactor. In some embodiments of the method, the NGL stream may be formed by the combination of a fresh natural gas liquid feed, the saturated or hydrogenated C5 hydrocarbon stream produced in the first hydrogenation reactor, and the saturated or hydrogenated C4 hydrocarbon stream produced in the second hydrogenation reactor.

[0007] In some embodiments, the method may further include supplying the C4 hydrocarbons separated from the pyrolysis product stream to a butadiene and 1-butene processing unit to produce a butadiene stream, a 1-butene stream, and a C4 raffinate stream; supplying the C4 raffinate stream to the first hydrogenation reactor or the second hydrogenation reactor to produce a saturated or hydrogenated C4 hydrocarbon stream; and supplying the saturated or hydrogenated C4 hydrocarbon stream to the reverse isomerization unit. In some embodiments, the method may further include separating C4 hydrocarbons from the pyrolysis product stream or a portion thereof in a debutanizer unit to produce a separated C4 hydrocarbon stream; and supplying the separated C4 hydrocarbon stream to the butadiene and 1-butene processing unit.

[0008] In some embodiments, the method may further comprise supplying a pyrolysis product stream to a product recovery section of a separation train, which may be operated to separate propylene and ethylene and / or C2 and C3 hydrocarbons from the pyrolysis product stream to produce a C4+ hydrocarbon stream; supplying the C4+ hydrocarbon stream to a debutanizer to produce a separated C4 hydrocarbon stream and a C5+ hydrocarbon stream; supplying the C5+ hydrocarbon stream to a depentanizer to produce a separated C5 hydrocarbon stream (i.e., a C5 raffinate stream) and a C6+ hydrocarbon stream; and supplying the separated C5 hydrocarbon stream to a first hydrogenation reactor. In some embodiments, the method may further comprise supplying the C5+ hydrocarbon stream or the separated C5 hydrocarbon stream to a gas hydrotreating reactor, and then supplying the C5 hydrocarbon stream to the first hydrogenation reactor. In some embodiments, the reverse isomerization unit operates at a temperature of about 240 °C to about 440 °C and a pressure of about 15 bar to about 30 bar.

[0009] The present invention also provides a method for producing light olefins from an NGL stream, which may comprise: hydrogenating a recycled C5 stream to produce a saturated recycled C5 stream, the recycled C5 stream being derived from the pyrolysis of a liquefied natural gas stream; isomerizing the hydrogenated recycled C5 stream and iso-C5 from a fresh liquefied natural gas stream to produce an isomerized hydrocarbon stream; and pyrolyzing the isomerized hydrocarbon stream to produce one or more light olefins and one or more additional pyrolysis products. In some embodiments, the method may further comprise hydrogenating a recycled C4 stream and a recycled C5 stream to produce a hydrogenated recycled mixed C4 and C5 stream, the recycled C4 stream and the recycled C5 stream being derived from the pyrolysis of a liquefied natural gas stream; isomerizing the hydrogenated recycled mixed C4 and C5 stream and a fresh liquefied natural gas stream to produce an isomerized hydrocarbon stream; and pyrolyzing the isomerized hydrocarbon stream to produce one or more light olefins and one or more pyrolysis products.

[0010] In some embodiments, the recycled C5 stream may be separated from one or more pyrolysis products. In some embodiments, the recycled C4 stream may be separated from one or more pyrolysis products. In some embodiments, the method may further comprise separating one or more light olefins from one or more pyrolysis products. In some embodiments, the method may further comprise feeding one or more additional pyrolysis products to a debutanizer to produce a recycled C4 stream and a debutanized hydrocarbon stream. In some embodiments, the method may further comprise feeding the debutanized hydrocarbon stream to a gas hydrotreating (GHT) reactor to produce a treated debutanized hydrocarbon stream; and feeding the treated debutanized hydrocarbon stream to a depentanizer to produce a recycled C5 stream. In some embodiments, the recycled C5 stream is a pentene-rich stream and the hydrogenated recycled C5 stream is a pentane-rich stream. In some embodiments, the recycled C4 stream is a butene-rich stream and the hydrogenated recycled mixed C4 and C5 stream is a pentane- and butane-rich stream.

[0011] The present invention provides a system for producing light olefins from a liquefied natural gas stream. The system may include: a reverse isomerization unit operable to receive a liquefied natural gas (NGL) stream, the reverse isomerization unit further operable to isomerize the NGL stream to produce a n-pentane-enriched NGL stream; a liquid furnace or one or more pyrolysis furnaces operable to receive the n-pentane-enriched NGL stream, the liquid furnace or one or more pyrolysis furnaces further operable to pyrolyze the n-pentane-enriched NGL stream to produce a pyrolysis product stream comprising C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons; a separation train operable to separate the C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons from the pyrolysis product stream; and a first hydrogenation reactor operable to receive the separated C5 hydrocarbons or a portion thereof, the first hydrogenation reactor further operable to hydrogenate the separated C5 hydrocarbons or a portion thereof to produce a saturated or hydrogenated C5 hydrocarbon stream; the reverse isomerization unit further operable to receive the saturated or hydrogenated C5 hydrocarbon stream.

[0012] In some embodiments of the system, recycling the saturated or hydrogenated C5 hydrocarbon stream to the reverse isomerization unit increases the light olefin yield, particularly the ethylene and / or propylene yield, of the liquid furnace. In some embodiments of the system, the NGL stream may be formed by the combination of a fresh liquefied natural gas feed and the saturated or hydrogenated C5 hydrocarbon stream produced in the first hydrogenation reactor. In some embodiments, the system may further include a second hydrogenation reactor operable to receive the separated C4 hydrocarbons or a portion thereof. The second hydrogenation reactor is further operable to hydrogenate the separated C4 hydrocarbons or a portion thereof to produce a saturated or hydrogenated C4 hydrocarbon stream. The reverse isomerization unit is operable to receive the saturated or hydrogenated C4 hydrocarbon stream produced by the second hydrogenation reactor.

[0013] In some embodiments of the system, the first hydrogenation reactor may be configured to receive the separated C4 hydrocarbons or a portion thereof. The first hydrogenation reactor is further operable to hydrogenate the separated C4 hydrocarbons or a portion thereof to produce a combined saturated or hydrogenated C4 hydrocarbon and saturated or hydrogenated C5 hydrocarbon stream. The reverse isomerization unit may be configured to receive the combined saturated or hydrogenated C4 and C5 hydrocarbon stream. In some embodiments of the system, the NGL stream may be formed by the combination of a fresh liquefied natural gas feed and the combined saturated or hydrogenated C4 and C5 hydrocarbon stream produced in the first hydrogenation reactor. In some embodiments of the system, the NGL stream may be formed by the combination of a fresh liquefied natural gas feed, the saturated or hydrogenated C5 hydrocarbon stream produced in the first hydrogenation reactor, and the saturated or hydrogenated C4 hydrocarbon stream produced in the second hydrogenation reactor.

[0014] In some embodiments, the system may further include a butadiene and 1-butene processing unit operable to receive C4 hydrocarbons separated from the pyrolysis product stream. The butadiene and 1-butene processing unit may also be operable to produce a butadiene stream, a 1-butene stream, and a C4 raffinate stream. The first hydrogenation reactor or the second hydrogenation reactor may be operable to receive the C4 raffinate stream and produce a saturated (hydrogenated) C4 hydrocarbon stream. The reverse isomerization unit may be operable to receive the saturated (hydrogenated) C4 hydrocarbon stream produced by the first or second hydrogenation reactor.

[0015] In some embodiments, the system may further include a debutanizer unit operable to receive the pyrolysis product stream or a portion thereof. The debutanizer unit may also be operable to separate C4 hydrocarbons from the pyrolysis product stream to produce a separated C4 hydrocarbon stream. The butadiene and 1-butene processing unit may also be operable to receive the separated C4 hydrocarbon stream produced by the debutanizer unit.

[0016] In some embodiments, the separation sequence of the system may include a product recovery section configured to receive the pyrolysis product stream produced by the liquid furnace, the product recovery section also being configured to separate propylene and ethylene (C2 and C3 hydrocarbons) from the pyrolysis product stream to produce a C4+ hydrocarbon stream; a debutanizer tower configured to receive the C4+ hydrocarbon stream produced by the product recovery section, the debutanizer tower also being configured to debutanize the C4+ hydrocarbon stream to produce a separated C4 hydrocarbon stream and a C5+ hydrocarbon stream; and a depentanizer tower configured to receive the C5+ hydrocarbon stream produced by the debutanizer tower, the depentanizer tower also being configured to depentanize the C5+ hydrocarbon stream to produce a separated C5 hydrocarbon (raffinate) stream and a C6+ hydrocarbon stream. In such embodiments, the first hydrogenation reactor may be operable to receive the separated C5 hydrocarbon stream produced by the depentanizer tower.

[0017] In some embodiments of the system, the product recovery section may include a deethanizer tower operable to receive the pyrolysis product stream or a portion thereof and produce a separated C2 hydrocarbon stream; and a depropanizer tower operable to receive the pyrolysis product stream or a portion thereof and produce a separated C3 hydrocarbon stream. The separated C2 hydrocarbon stream may contain ethylene and the separated C3 hydrocarbon stream may contain propylene. The deethanizer tower may be configured to produce a C3+ hydrocarbon stream, and the depropanizer tower may be configured to receive the C3+ hydrocarbon stream produced by the deethanizer tower and produce a separated C3 hydrocarbon stream and a C4+ hydrocarbon stream. In some embodiments, the system may further include a gas hydrotreating reactor configured to receive the C5+ hydrocarbon stream produced by the debutanizer tower or the separated C5 hydrocarbon stream (i.e., the C5 raffinate stream) produced by the depentanizer tower, and then supply the C5 hydrocarbon stream to the first hydrogenation reactor. In some embodiments of the system, the reverse isomerization unit operates at a temperature of about 240°C to about 440°C and a pressure of about 15 bar to about 30 bar.

[0018] The present invention also provides a system for producing light olefins from an NGL stream, which may include: a hydrogenation reactor operable to receive a recycled C5 stream resulting from the pyrolysis of a liquefied natural gas stream and operable to hydrogenate the recycled C5 stream to produce a hydrogenated recycled C5 stream; a reverse isomerization reactor operable to receive a fresh liquefied natural gas stream and the hydrogenated recycled C5 stream, the reverse isomerization reactor also being operable to isomerize the combined fresh liquefied natural gas stream and hydrogenated recycled C5 stream to produce an isomerized hydrocarbon stream; and one or more pyrolysis furnaces operable to receive the isomerized hydrocarbon stream and pyrolyze the isomerized hydrocarbon stream to produce one or more light olefins and one or more pyrolysis products.

[0019] In some embodiments of the system, the hydrogenation reactor may also be operable to receive a recycled C4 stream resulting from the pyrolysis of a liquefied natural gas stream and hydrogenate the combined recycled C4 and C5 streams to produce a hydrogenated recycled mixed C4 and C5 stream. The reverse isomerization reactor is operable to receive a fresh liquefied natural gas stream and the hydrogenated recycled mixed C4 and C5 stream. The reverse isomerization reactor is also operable to isomerize the combined fresh liquefied natural gas stream and hydrogenated recycled mixed C4 and C5 stream to produce an isomerized hydrocarbon stream. In some embodiments, the system may also include one or more separators operable to separate one or more light olefins from one or more pyrolysis products. In some embodiments, the system may also include a debutanizer tower operable to receive one or more additional pyrolysis products and produce a recycled C4 stream and a debutanized hydrocarbon stream.

[0020] In some embodiments, the system may also include a gas hydrogenation treatment (GHT) reactor operable to receive the debutanized hydrocarbon stream from the debutanizer tower and produce a treated debutanized hydrocarbon stream. In some embodiments, the system may also include a de-pentanizer tower operable to receive the treated debutanized hydrocarbon stream and produce a recycled C5 stream and a C6-C8 stream. In some embodiments, the recycled C5 stream may be a pentene-rich stream and the hydrogenated recycled C5 stream may be a pentane-rich stream. In some embodiments of the system, the recycled C4 stream may be a butene-rich stream. In some embodiments of the system, the hydrogenated recycled mixed C4 and C5 stream may be a pentane-rich and butane-rich stream.

[0021] Other aspects and advantages of these exemplary embodiments and other embodiments are also discussed in detail herein. In addition, it is to be understood that the foregoing information and the following detailed description provide illustrative examples of various aspects and embodiments and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed aspects and embodiments. Accordingly, these and other objects of the present invention, together with the advantages and features, will become apparent by reference to the following description and the drawings. In addition, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and may exist in various combinations and permutations. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the detailed description, serve to explain the principles of the embodiments discussed herein. The structural details of the present invention are not attempted to be shown in more detail than is necessary for a fundamental understanding of the embodiments discussed herein and the various ways in which they may be practiced. By convention, the various features of the drawings discussed below are not necessarily drawn to scale. The dimensions of the various features and elements in the drawings may be enlarged or reduced to more clearly show the embodiments of the present invention.

[0023] Figure 1 is a diagram of a system and method for producing light olefins from an NGL stream according to an exemplary embodiment of the present invention, which includes feeding an unhydrogenated C4 and C5 hydrocarbon stream separated from a pyrolysis product stream to a single hydrogenation reactor, and then recycling the hydrogenated C4 / C5 hydrocarbon stream to a reverse isomerization reactor.

[0024] Figure 2 is a diagram of a system and method for producing light olefins from an NGL stream according to an exemplary embodiment of the present invention, which includes feeding an unhydrogenated C5 hydrocarbon stream separated from a pyrolysis product stream to a hydrogenation reactor, and then recycling the hydrogenated C5 hydrocarbon stream to a reverse isomerization reactor. DETAILED DESCRIPTION

[0025] The present invention describes various embodiments related to processes, methods, and systems for integrating petrochemical and refining operations. Additional embodiments may be described and disclosed.

[0026] In the following description, numerous details are set forth in order to provide a thorough understanding of the various embodiments. In other instances, well-known processes, equipment, and systems may not be described in particular detail in order to avoid unnecessarily obscuring the various embodiments. Additionally, certain features or details of the various embodiments may be omitted in the description in order not to obscure the various embodiments.

[0027] The description may use the phrases "in some embodiments", "in various embodiments", "in one embodiment", or "in embodiments", which may each refer to one or more of the same or different embodiments. Additionally, the terms "comprising", "including", "having", and the like used with respect to the embodiments of the present invention are synonyms.

[0028] The term "about" or "approximately" is defined as being close to as understood by a person of ordinary skill in the art. In a non-limiting embodiment, the term is defined as within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0029] When used in the claims and / or the specification, the terms "reduce", "decrease" or any variation thereof include any measurable reduction or complete inhibition for achieving the desired result.

[0030] When used in conjunction with any of the terms "comprising", "including", "containing" or "having" in the claims or the specification, the use of the word "a" or "an" may mean "one", but it is also consistent with the meanings of "one or more", "at least one" and "more than one". The terms "weight %", "volume %" or "mole %" refer respectively to the weight, volume or mole percentage of a component based on the total weight, total volume or total moles of the material including the component. In a non-limiting example, 10 grams of a component in 100 grams of material is a 10 weight % component.

[0031] The words "comprising", "having", "including" or "containing" and any form thereof are inclusive or open-ended and do not exclude additional unrecited elements or method steps.

[0032] Disclosed herein are systems and methods for increasing the light olefin yield by upgrading feedstock prior to injecting into a liquid furnace and pyrolyzing an NGL stream in a liquid furnace. Specifically, prior to being fed to one or more pyrolysis furnaces, a fresh NGL stream may be mixed or combined with a rich n-C5 feedstock stream produced from a recycled C5 hydrocarbon stream separated from the pyrolysis product stream by one or more hydrogenation reactors.

[0033] Preprocessing an NGL hydrocarbon feedstock using one or more hydrogenation reactors and reverse isomerization reactors provides a rich n-C5 feedstock stream to the pyrolysis furnace, thereby increasing the overall productivity of light olefins, particularly ethylene.

[0034] Figure 1 FIG. is a diagram of an exemplary system 100 and method for producing ethylene and other light olefins from a liquefied natural gas feed stream 105 according to an exemplary embodiment of the present invention, which includes feeding unhydrogenated C4 and C5 hydrocarbon streams 178, 185 separated from the pyrolysis product stream 125 by a separation train 128 to a single hydrogenation reactor 190, and then recycling the hydrogenated C4 / C5 hydrocarbon stream 195 to a reverse isomerization reactor 110. As Figure 1 depicted, the system 100 may include one or more reverse isomerization reactors, such as reverse isomerization reactor 110. The reverse isomerization reactor 110 may be operated to receive a liquefied natural gas (NGL) stream 101, such as a fresh NGL feed stream 105, and isomerize the NGL feed stream 101 to produce an isomerized hydrocarbon stream 115 or a n-pentane enriched NGL stream 115.

[0035] As Figure 1 depicted in, the reverse isomerization reactor 110 may be fluidly connected to one or more pyrolysis furnaces, such as the liquid furnace 120. The liquid furnace 120 may be operated to receive the isomerized hydrocarbon stream 115 or the n-pentane enriched NGL stream 115 produced by the reverse isomerization reactor 110. The liquid furnace 120 may also be operated to pyrolyze the isomerized hydrocarbon stream 115 or the n-pentane enriched NGL stream 115 to produce a pyrolysis product stream 125. In addition to other hydrocarbon and chemical components, the pyrolysis product stream 125 may include C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons. As used herein, the term "C6+ hydrocarbons" refers to hydrocarbons having six or more carbon atoms. Similar terms such as "C3+ hydrocarbons", "C4+ hydrocarbons", and "C5+ hydrocarbons" also refer to hydrocarbons having three or more carbon atoms, four or more carbon atoms, and five or more carbon atoms, respectively.

[0036] The system 100 may also include a separation train 128 that may be operated to separate the C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons in the pyrolysis product stream 125. Thus, the separation train 128 is fluidly connected to the pyrolysis furnace 120 and may be operated to receive the pyrolysis product stream 125 produced by the pyrolysis furnace 120. As Figure 1 depicted in, the separation train 128 in the system 100 may include a product separation section 130, a debutanizer 140, a de-pentanizer 180, a butadiene and 1-butene processing unit 170, and a stabilizer / demethanizer 160. The product separation section 130 of the separation train 128 may be fluidly connected to the liquid furnace 120 and may be operated to receive the pyrolysis product stream 125 produced by the liquid furnace 120. The product separation section 130 may include components that may be operated to separate light olefin products, such as ethylene and propylene, and other C2 and C3 hydrocarbons produced by pyrolysis in the liquid furnace 120. Thus, the product separation section 130 may include a de-ethanizer and a de-propanizer. After product separation, the resulting C4+ hydrocarbon stream 135 (e.g., the de-propanizer bottoms stream) may be supplied to the debutanizer 140.

[0037] As Figure 1As depicted, system 100 may include a debutanizer 140 that is fluidly connected to the product separation section 130 and operable to receive the C4+ hydrocarbon stream 135 produced by the product separation section 130. The debutanizer 140 may be operable to separate C4 hydrocarbons from the C4+ hydrocarbon stream 135 to produce a separated C4 hydrocarbon stream 145 and a C5+ hydrocarbon stream 146. The separation sequence 128 of system 100 may also include a butadiene and 1-butene processing unit 170 that is fluidly connected to the debutanizer 140 and operable to receive the separated C4 hydrocarbon stream 145. The butadiene and 1-butene processing unit 170 may also be operable to process the separated C4 hydrocarbon stream 145 to produce a butadiene product stream 171, a 1-butene product stream 172, a residue 173 for dehydrogenation or other uses, and a C4 residue stream 175. The butadiene and 1-butene processing unit 170 may be fluidly connected to the unhydrogenated mixed C4 sphere 177 and the C4 / C5 hydrogenation reactor 190 or the first hydrogenation reactor 190.

[0038] System 100 may also include a gas hydrogenation treatment (GHT) reactor 150 that is fluidly connected to the debutanizer 140 such that the GHT reactor 150 is operable to receive the C5+ hydrocarbon stream 146 produced by the debutanizer 140. The GHT reactor 150 may be operable to hydrogenate the C5+ hydrocarbon stream 146 and produce a hydrogenated C5+ hydrocarbon stream 155. As Figure 1 depicted, the GHT reactor 150 is fluidly connected to a stabilizer / deoctanizer 160. The stabilizer / deoctanizer 160 may be operable to receive the hydrogenated C5+ hydrocarbon stream 155 produced by the GHT reactor 150 and produce a fuel gas stream 163, a C9+ residue stream 161, a wash oil stream 162, and a residual C5+ hydrocarbon stream 165.

[0039] The separation sequence 128 of system 100 also includes a depentanizer 180 that is fluidly connected to the stabilizer / deoctanizer 160 and operable to receive the residual C5+ hydrocarbon stream 165 produced by the stabilizer / deoctanizer 160. The depentanizer 180 may be operable to separate C5 hydrocarbons from the residual C5+ hydrocarbon stream 165 to produce a separated C5 hydrocarbon stream 185 or a C5 residue stream 185 and a C6+ hydrocarbon stream 186. The separated C5 hydrocarbon stream or the C5 residue stream 185 may be supplied to the C4 / C5 hydrogenation reactor 190 in the form of a combined C4 / C5 residue stream 178 or a combined separated C4 / C5 stream 178.

[0040] The C4 / C5 hydrogenation reactor 190 is operable to receive a C4 raffinate stream 175 or a separated C4 stream 178 from the unhydrogenated mixed C4 sphere 177 and a separated C5 hydrocarbon stream or a C5 raffinate stream 185 in the form of a combined separated C4 / C5 stream 178. The C4 / C5 hydrogenation reactor 190 is also operable to hydrogenate or saturate the combined separated C4 / C5 stream 178 to produce a saturated or hydrogenated C4 / C5 hydrocarbon stream 195. The C4 / C5 hydrogenation reactor 190 is fluidly connected to the reverse isomerization reactor 110 such that the combined saturated / hydrogenated C4 / C5 hydrocarbon stream 195 can be supplied to the reverse isomerization reactor 110 as a separate feed stream to the reverse isomerization reactor 110 or as part of a combined stream with the fresh NGL feed stream 105 in the form of an NGL stream 101.

[0041] Although Figure 1 a single C4 / C5 hydrogenation reactor 190 is depicted, in other embodiments of the system 100, the C4 / C5 hydrogenation reactor 190 can be configured to be replaced by any number of hydrogenation reactors that receive unhydrogenated C4 and C5 streams separated from the pyrolysis product stream 125. In some embodiments, the single C4 / C5 hydrogenation reactor 190 can be replaced by a first hydrogenation reactor that is operable to receive a separated C5 hydrocarbon stream or a C5 raffinate stream and hydrogenate / saturate it and a second hydrogenation reactor that is operable to receive a separated C4 hydrocarbon stream or a C4 raffinate stream and hydrogenate / saturate it. The output streams of the first and second hydrogenation reactors can be combined to form a saturated / hydrogenated C4 / C5 hydrocarbon stream 195 and supplied to the reverse isomerization reactor 110 either individually or as a combined feed stream with the fresh NGL feed stream 105 to form an NGL feed 101.

[0042] Figure 2 is a diagram of an exemplary system 200 and method for producing ethylene and other light olefins from a liquefied natural gas feed stream 205 in accordance with an exemplary embodiment of the present invention, which includes feeding an unhydrogenated C5 hydrocarbon stream 285 separated from the pyrolysis product stream 225 through a separation sequence 228 to a C5 hydrogenation reactor 290, and then recycling the hydrogenated / saturated C5 hydrocarbon stream 295 to the reverse isomerization reactor 210. As Figure 2 depicted, the system 200 can include one or more reverse isomerization reactors, such as the reverse isomerization reactor 210. The reverse isomerization reactor 210 is operable to receive a liquefied natural gas (NGL) stream 201, such as a fresh NGL feed stream 205, and isomerize the NGL feed stream 201 to produce an isomerized hydrocarbon stream 215 or a n-pentane-enriched NGL stream 215.

[0043] As Figure 2As depicted, the reverse isomerization reactor 210 may be fluidly connected to one or more pyrolysis furnaces, such as the liquid furnace 220. The liquid furnace 220 may be operated to receive the isomerized hydrocarbon stream 215 or the n-pentane enriched NGL stream 215 produced by the reverse isomerization reactor 210. The liquid furnace 220 may also be operated to pyrolyze the isomerized hydrocarbon stream 215 or the n-pentane enriched NGL stream 215 to produce a pyrolysis product stream 225. In addition to other hydrocarbon and chemical components, the pyrolysis product stream 225 may include C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons.

[0044] The system 200 may also include a separation train 228 that may be operated to separate C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons in the pyrolysis product stream 225. Thus, the separation train 228 is fluidly connected to the pyrolysis furnace 220 and may be operated to receive the pyrolysis product stream 225 produced by the pyrolysis furnace 220. As Figure 2 depicted, the separation train 228 in the system 200 may include a product separation section 230, a debutanizer 240, a de-pentanizer 280, and a stabilizer / demethanizer 260. The product separation section 230 of the separation train 228 may be fluidly connected to the liquid furnace 220 and may be operated to receive the pyrolysis product stream 225 produced by the liquid furnace 220. The product separation section 230 may include components that may be operated to separate light olefin products, such as ethylene and propylene, and other C2 and C3 hydrocarbons produced by pyrolysis in the liquid furnace 220. Thus, the product separation section 230 may include a de-ethanizer and a de-propanizer. After product separation, the resulting C4+ hydrocarbon stream 235 (e.g., the de-propanizer bottoms stream) may be supplied to the debutanizer 240.

[0045] As Figure 2 depicted, the system 200 may include a debutanizer 240 that is fluidly connected to the product separation section 230 and may be operated to receive the C4+ hydrocarbon stream 235 produced by the product separation section 230. The debutanizer 240 may be operated to separate C4 hydrocarbons from the C4+ hydrocarbon stream 235, producing a separated C4 hydrocarbon stream 245 and a C5+ hydrocarbon stream 246. The system 200 may also include a gas hydrotreating (GHT) reactor 250 that is fluidly connected to the debutanizer 240 such that the GHT reactor 250 may be operated to receive the C5+ hydrocarbon stream 246 produced by the debutanizer 240. The GHT reactor 250 may be operated to hydrotreat the C5+ hydrocarbon stream 246 and produce a hydrotreated C5+ hydrocarbon stream 255. As Figure 2 depicted, the GHT reactor 250 is fluidly connected to the stabilizer / demethanizer 260. The stabilizer / demethanizer 260 may be operated to receive the hydrotreated C5+ hydrocarbon stream 255 produced by the GHT reactor 250 and produce a fuel gas stream 263, a C9+ residue stream 261, a wash oil stream 262, and a residual C5+ hydrocarbon stream 265.

[0046] The separation train 228 of system 200 also includes a debutanizer 280 that is fluidly connected to the stabilizer / demethanizer 260 and operable to receive the residual C5+ hydrocarbon stream 265 produced by the stabilizer / demethanizer 260. The debutanizer 280 is operable to separate C5 hydrocarbons from the residual C5+ hydrocarbon stream 265 to produce a separated C5 hydrocarbon stream 285 or a C5 raffinate stream 285 and a C6+ hydrocarbon stream 286. The separated C5 hydrocarbon stream or the C5 raffinate stream 285 can be supplied to a C5 hydrogenation reactor 290 (e.g., the first hydrogenation reactor 290).

[0047] The C5 hydrogenation reactor 290 is operable to receive the separated C5 hydrocarbon stream or the C5 raffinate stream 285 produced by the debutanizer 280, and hydrogenate or saturate the separated C5 hydrocarbon stream or the C5 raffinate stream 285 to produce a saturated or hydrogenated C5 hydrocarbon stream 295. The C5 hydrogenation reactor 290 is fluidly connected to the reverse isomerization reactor 210 such that the saturated / hydrogenated C5 hydrocarbon stream 295 can be supplied to the reverse isomerization reactor 210 as a separate feed stream to the reverse isomerization reactor 210 or as part of a combined stream with the fresh NGL feed 205 in the form of an NGL stream 201.

[0048] Example

[0049] The examples provided below illustrate selected aspects of various methods and systems for producing light olefins from an NGL stream and do not limit the scope of the disclosure in any way.

[0050] Example 1

[0051] Figure 1 The hydrocarbon yields of the system 100 depicted in are shown in Table 1 as determined by simulation. As shown in Table 1, from an exemplary NGL fresh feed containing 9.48 metric tons per hour (T / hr) of isopentane and 13.35 T / hr of n-pentane, the system 100 produced 9.93 T / hr of ethylene and 3.75 T / hr of propylene at the furnace outlet.

[0052] Table 1

[0053]

[0054]

[0055] Example 2

[0056] Figure 2 The hydrocarbon yields of the system 200 depicted in are shown in Table 2 as determined by simulation. As shown in Table 2, from an NGL fresh feed containing 9.48 metric tons per hour (T / hr) of isopentane and 13.35 T / hr of n-pentane, the system 200 produced 11.99 T / hr of ethylene and 4.49 T / hr of propylene at the furnace outlet. Thus, compared to Figure 1The C4 / C5 hydrogenation system 100 (Example 1) depicted in Figure 2 The C5 hydrogenation of the recycled C5 hydrocarbon stream separated from the pyrolysis product stream according to the system and method depicted in

[0057] Table 2

[0058]

[0059]

[0060] When the scope is disclosed herein, any range starting from a lower limit can be combined with any upper limit to recite a range not expressly recited, and any range starting from a lower limit can be combined with any other lower limit to recite a range not expressly recited. In the same manner, any range starting from an upper limit can be combined with any other upper limit to recite a range not expressly recited. Additionally, although not expressly recited, the reference to a value specified in a range includes every value within that range. Thus, each point or single value can serve as its own lower or upper limit, combined with any other point or single value or any other lower or upper limit, to recite a range not expressly recited.

[0061] Other objects, features, and advantages of the present invention will become apparent from the foregoing drawings, detailed description, and examples. It should be understood that the drawings, detailed description, and examples, although indicating specific embodiments of the present invention, are given by way of example only and are not intended to be limiting. In other embodiments, the features of a specific embodiment can be combined with the features of other embodiments. For example, the features of one embodiment can be combined with the features of any of the other embodiments. In other embodiments, additional features can be added to the specific embodiments described herein.

Claims

1. A method for producing light olefins from a liquefied natural gas stream, the method comprising: Supplying a liquefied natural gas (NGL) stream to a reverse isomerization unit to produce a n-pentane-enriched NGL stream; Supplying the n-pentane-enriched NGL stream to a liquid furnace to produce a pyrolysis product stream, the pyrolysis product stream comprising C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons; Separating the C2 hydrocarbons, the C3 hydrocarbons, the C4 hydrocarbons, the C5 hydrocarbons, and the C6+ hydrocarbons in the pyrolysis product stream in a separation sequence; Supplying the separated C5 hydrocarbons or a portion thereof to a first hydrogenation reactor to produce a saturated C5 hydrocarbon stream; and Recycling the saturated C5 hydrocarbon stream to the reverse isomerization unit.

2. The method according to claim 1, wherein recycling the saturated C5 hydrocarbon stream to the reverse isomerization unit increases the ethylene and / or propylene yield of the liquid furnace.

3. The method according to claim 1 or claim 2, wherein the NGL stream is formed by the combination of a fresh liquefied natural gas feed and the saturated C5 hydrocarbon stream produced in the first hydrogenation reactor.

4. The method according to any one of claims 1-3, further comprising: Supplying the separated C4 hydrocarbons or a portion thereof to a second hydrogenation reactor to produce a saturated C4 hydrocarbon stream; Recycling the saturated C4 hydrocarbon stream to the reverse isomerization unit.

5. The method according to any one of claims 1-3, further comprising: Supplying the separated C4 hydrocarbons or a portion thereof to the first hydrogenation reactor to produce a combined saturated C4 and saturated C5 hydrocarbon stream; And Recycling the combined saturated C4 and C5 hydrocarbon stream to the reverse isomerization unit.

6. The method according to claim 5, wherein the NGL stream is formed by the combination of a fresh liquefied natural gas feed and the combined saturated C4 and C5 hydrocarbon stream produced in the first hydrogenation reactor.

7. The method according to claim 4, wherein the NGL stream is formed by the combination of a fresh liquefied natural gas feed, the saturated C5 hydrocarbon stream produced in the first hydrogenation reactor, and the saturated C4 hydrocarbon stream produced in the second hydrogenation reactor.

8. The method according to any one of claims 1-7, further comprising: Supplying the C4 hydrocarbons separated from the pyrolysis product stream to a butadiene and 1-butene processing unit to produce a butadiene stream, a 1-butene stream, and a C4 residue stream; Supplying the C4 residue stream to the first hydrogenation reactor or the second hydrogenation reactor to produce a saturated C4 hydrocarbon stream; and Supplying the saturated C4 hydrocarbon stream to the reverse isomerization unit.

9. The method according to claim 8, further comprising: Separating C4 hydrocarbons from the pyrolysis product stream or a portion thereof in a debutanizer unit to produce a separated C4 hydrocarbon stream; And Supplying the separated C4 hydrocarbon stream to the butadiene and 1-butene processing unit.

10. The method according to any one of claims 1-9, further comprising: Supply the pyrolysis product stream to the product recovery section of the separation train, which is operable to separate propylene and ethylene from the pyrolysis product stream to produce a C4+ hydrocarbon stream; Supply the C4+ hydrocarbon stream to a debutanizer to produce a separated C4 hydrocarbon stream and a C5+ hydrocarbon stream; Supply the C5+ hydrocarbon stream to a depentanizer to produce a separated C5 hydrocarbon stream and a C6+ hydrocarbon stream; and Supply the separated C5 hydrocarbon stream to the first hydrogenation reactor.

11. The method according to any one of claims 1-10, further comprising: Supply the C5+ hydrocarbon stream or the separated C5 hydrocarbon stream to a gas hydrogenation treatment reactor, and then supply the C5 hydrocarbon stream to the first hydrogenation reactor.

12. A system for producing light olefins from a liquefied natural gas stream, the system comprising: A reverse isomerization unit operable to receive a liquefied natural gas (NGL) stream, the reverse isomerization unit further operable to isomerize the NGL stream to produce a n-pentane-enriched NGL stream; A liquid furnace operable to receive the n-pentane-enriched NGL stream, the liquid furnace further operable to pyrolyze the n-pentane-enriched NGL stream to produce a pyrolysis product stream comprising C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, and C6+ hydrocarbons; A separation train operable to separate the C2 hydrocarbons, the C3 hydrocarbons, the C4 hydrocarbons, the C5 hydrocarbons, and the C6+ hydrocarbons in the pyrolysis product stream; and A first hydrogenation reactor operable to receive the separated C5 hydrocarbon or a portion thereof, the first hydrogenation reactor further operable to hydrogenate the separated C5 hydrocarbon or a portion thereof to produce a saturated C5 hydrocarbon stream; The reverse isomerization unit is further operable to receive the saturated C5 hydrocarbon stream.

13. The system according to claim 12, wherein the separation train comprises: A product recovery section configured to receive the pyrolysis product stream produced by the liquid furnace, the product recovery section further configured to separate propylene and ethylene from the pyrolysis product stream to produce a C4+ hydrocarbon stream; A debutanizer configured to receive the C4+ hydrocarbon stream produced by the product recovery section, the debutanizer further configured to debutanize the C4+ hydrocarbon stream to produce a separated C4 hydrocarbon stream and a C5+ hydrocarbon stream; and A depentanizer configured to receive the C5+ hydrocarbon stream produced by the debutanizer, the depentanizer further configured to depentanize the C5+ hydrocarbon stream to produce a separated C5 hydrocarbon stream and a C6+ hydrocarbon stream; wherein the first hydrogenation reactor is operable to receive the separated C5 hydrocarbon stream produced by the depentanizer.

14. The system according to claim 12 or claim 13, further comprising: A gas hydrogenation treatment reactor configured to receive the C5+ hydrocarbon stream produced by the debutanizer or the separated C5 hydrocarbon stream produced by the depentanizer, and then supply the C5 hydrocarbon stream to the first hydrogenation reactor.

15. The system according to claim 12 or claim 13 or claim 14, wherein the reverse isomerization unit operates at a temperature of about 240 °C to about 440 °C and a pressure of about 15 bar to about 30 bar.

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